The present invention relates to transplantation of human fetal pancreatic cells to treat Type 1 diabetes mellitus. More particularly, the invention relates to the use of a human cytokine, hepatocyte growth factor/scatter factor, to induce ex vivo the proliferation and differentiation of fetal pancreatic cells prior to their transplantation into a diabetic subject.
Type 1 (insulin-dependent) diabetes mellitus is characterized, inter alia, by a loss of insulin-producing Beta (".beta.") cells and decompensation of metabolism following autoimmune aggression. Fisenharth, N. Eng. J. Med. 314: 1360 (1986); Sweane, Diabetologia 35: 193 (1992). Treatments of such patients have included primarily parenteral administration of bovine or porcine insulin or recombinant human insulin. This treatment, however, delays, but does not avoid, the pathological sequelae of this disease, and, in addition, requires multiple daily injections of insulin and/or the use of an indwelling catheter and an insulin pump.
Immunosuppressive treatment of patients, for example, with cyclosporin A or FK506 has also been used, but with only limited success. Immunosuppressive drugs produce toxic side effects, including the potential for infection as the result of suppression of the immune system.
Recently, adult human pancreatic islets have transplanted into patients in order to achieve independence from insulin injections. Scharp et al., Transplant. 51:76 (1991); Warnock et al., Diabetologia 34: 55 (1991). Despite these advances, the limited number of organ donors, the inadequate islet masses obtainable from most pancreases, and graft rejection problems have conspired to limit the general usefulness of this approach. Ricordi et al., Transplant. 53: 407 (1992).
An alternate source of pancreatic islets for transplantation is the fetal pancreas. This tissue is rich in undifferentiated .beta.-cells that can, at least in theory, grow and mature after transplantation. Tuch et al., Diabetes 35:464 (1986). While the immature immune system of the fetus reduces the likelihood of fetal islet rejection by the recipient, problems relating to the limited availability of suitable fetal pancreases and to the immaturity of the insulin-producing cells in such tissues continue to hinder success in this approach. For a review, see Andersson, Transplantation Revs. 6: 20 (1992).
Hepatocyte Growth Factor ("HGF"), a 87 kDa two-chain glycoprotein cytokine first identified in rodent and human plasma and rodent blood platelets, is a potent hepatocyte mitogen. Rubin et al., Biochem. Biophys. Acta 1155: 357 (1993). HGF is apparently identical to a fibroblast secretory protein referred to as Scatter Factor ("SF") known to dissociate and increase the motility of epithelial cells. Gherardi et al., Nature 346:228 (1990); Weidner et al., Proc. Nat'l. Acad. Sci. (USA) 88:7001 (1991); Furlong et al., J. Cell Sci. 100: 173 (1991); Naldini et al., EMBO J. 10:2867 (1991); Bhargava et al., Cell Growth Differ. 3:11 (1992). For this reason, "HGF/SF" is used here as the abbreviation of the name of this cytokine. For reviews of the biology of HGF/SF, see Strain, J. Endocrinol. 137: 1 (1993), Furlong, BioEssays 14: 613 (1992), and Rubin et al. (1993), above.
HGF has been purified to homogeneity and sequenced, and its gene has been cloned. Miyazawa et al., Biochem. Biophys. Res. Commun. 163: 967 (1989); Rubin et al., Proc. Nat'l Acad. USA 88: 415 (1991); Weidner et al., Sci. (USA) 88:7001 (1991); Nakamura et al., FEBS Lett. 224:311 (1987); Nakamura et al., Nature 342:440 (1989) Gohda et al., J. Clin. Invest. 81: 414 (1988), all of which are incorporated herein by reference.
Wolf et al., Hepatology 14: 488 (1991), identified HGF/SF in adult human pancreatic tissue by immunohistochemistry. However, the identifying signal was strong only in exocrine tissue, very weak in endocrine tissues, with no apparent differences between various cell types. In sharp contrast, Tsuda et al., Jpn. J. Cancer Res. 83: 1262 (1992), reported immunohistochemistry studies that identified HGF/SF in adult (human and rat) pancreatic, glucagon-producing A cells, but not in the exocrine pancreas. The authors concluded that this cytokine is primarily produced or stored in the A cells, and it was hypothesized that HGF/SF may act as a growth factor in a paracrine and an endocrine fashion. Yet DeFrances et al., Development. 116:387 (1992), demonstrated immunohistochemically the presence of HGF/SF in developing rat fetal pancreas with intense staining in acinar cells.